1. Field of the Invention
The present invention relates to a busbar through which a large current flows, the busbar including male-terminal-connecting portion having spring property, and to an electrical junction box incorporating this busbar.
2. Description of the Related Art
An electrical junction box, e.g., a relay box (R/B) mounted in an automobile or other vehicles comprises a busbar that includes male-terminal-connecting portions for connecting male tab terminals (male terminals) of a miniature fuse and a blade-type fuse to the busbar.
The male-terminal-connecting portion has a tuning-fork-like shape for clamping the male tab terminal to provide electrical connection.
The busbar is made of an electrically-conductive metal material having superior spring property (an electrically-conductive metal material having superior mechanical property) so that the male tab terminal is clamped by the male-terminal-connecting portion and electrically connected thereto.
The electrically-conductive metal material is copper alloy having the spring property so that the busbar ensures reliable electrical connection.
However, since the copper alloy is made of copper as the principal component and other metal or non-metal material, its electric conductivity is inferior to that of pure copper. Accordingly, in order that the large current is allowed to flow in the busbar, a cross section of the busbar has to be enlarged. This means that the busbar has relatively large dimensions.
Such a conventional busbar having relatively large dimensions may not be compatible with high yield ratio and mountability, i.e., the degree of how the busbar can be readily mounted to the electrical junction box.
In addition, a busbar made of pure copper in view of improved electric conductivity may fail to have sufficient spring property, and such insufficient spring property makes it difficult for the male-terminal-connecting portion to ensure reliable connection.
Japanese Patent Application Laid-Open Publication No. 2009-77485 discloses a busbar that addresses the above-identified drawbacks found in the conventional products.
As shown in FIG. 6, a busbar 1 comprises a first busbar component 2, a second busbar component 4, and a plurality of male-terminal-connecting portions 3 provided in the second busbar component 4. The first busbar component 2 is made of electrically-conductive metal material having superior electrical conductivity and serves as the busbar body. The second busbar component 4 is made of an electrically-conductive metal material having superior mechanical property and connected by welding to a predetermined portion of the first busbar component 2 as the busbar body.
The second busbar component 4 includes (i) a section dedicated to connecting a male tab terminal to the second busbar component 4, i.e., a male-terminal-connecting portion 3, and (ii) a portion 5 for welding of the second busbar component 4 to the first busbar component 2. This configuration allows the busbar 1 to increase the electric conductivity of the first busbar component 2 serving as the busbar body when compared with a conventional busbar, and thereby the dimensions can be reduced and at the same time reliable connection of the second busbar component 4 can be maintained in a sufficient level as in the conventional one. The busbar 1 improves its yield ratio and mountability with respect to the electrical junction box.
Although the busbar 1 disclosed in the patent literature PTL 1 is advantageous in the above aspects, improvement of the following aspects will make the busbar more advantageous. Specifically, since relatively large force acts upon the male-terminal-connecting portion 3 when the male tab terminal is inserted thereinto and detached therefrom, breakage or detachment of the second busbar component 4 from the first busbar component 2 may result if the connection (joining) provided at a portion b below the male-terminal-connecting portion 3 is incomplete or insufficient.
Also, when the accuracy of the connection (joining) between the first and second busbar components 2, 4 is not increased, the second busbar component 4 may be deviated from its intended position with respect to the male tab terminal to be connected thereto, and also may be deviated from its intended position with respect to the electrical junction box to which the second busbar component 4 is to be connected.
Also, it is more preferable to reduce the dimensions of the busbar 1 while ensuring that the large current can flow in the busbar 1.